The undercover Fort Worth police officer who mistakenly targeted a Dallas man in this week’s Texas Christian University drug busts possibly undermined the entire case with his “sloppy” police work, lawyers familiar with the case said Friday.

Authorities on Wednesday arrested 21 enrolled or former TCU students — including four current football players — in a highly publicized drug-trafficking case.

On Friday, a 22nd suspect, Hunter McLaughlin, 24, surrendered and was immediately released on bond. Some other suspects spent the day obtaining or meeting with attorneys. Initially, 18 people were known to have been arrested on Wednesday, but three others were taken into custody on the same day.

In sworn arrest affidavits, Officer J.C. Williams declared that “Austin Williams Carpenter” was one of the people from whom he purchased drugs three times. But the Austin Carpenter identified in the warrant, which included a photo and was released to the public, was not the person who allegedly dealt Williams the drugs.

The person erroneously named in the warrant is the great-grandson of Dallas businessman John W. Carpenter, who has a local freeway named after him. The 26-year-old’s mother is the daughter of the late Dolph Briscoe, a former Texas governor once considered the largest individual landowner in the state. The 26-year-old was not arrested, but his family has demanded a public apology from Fort Worth police for wrongly naming him a suspect.

The Austin Carpenter police really want is 19 and lives in Houston. On Friday, his Houston attorney, Joe David Wells, blasted Williams and the possible case against his client.

“In the event that the authorities in Tarrant County decide to pursue charges, I look forward to a vigorous cross-examination of the officer who swore under oath that he dealt with a different Austin Carpenter than my client,” Wells said.

He added that the use of photographs on all the arrest warrants trampled on the presumption of innocence of the suspects and could end up derailing all the cases. It is very unusual for photos of suspects to be part of an arrest warrant affidavit.

“Texas law does not require the inclusion of a photograph for the issuance of an arrest warrant,” Wells said. “The only reason for including a photograph in the warrant is for publicity. Their failed attempt at a photographic perp walk could result in acquittals of all of the students charged in this scandal.”

Terri Moore, a former prosecutor with the district attorney’s offices in Tarrant and Dallas counties, as well as the U.S. attorney’s office, agreed. She said Williams made a “major, major error” that will definitely harm Carpenter’s case and perhaps the others.

“He made a huge mistake, he stepped in it, and he’s going to have to eat it,” said Moore, now a defense attorney. “That screws up that case as far as that defendant goes.

“You sat down and looked at the photograph and you took that and swore to a judge that this was correct, and he relied on that to issue a warrant,” she said. “I’m not saying that it was a dishonest mistake, but it’s a huge mistake. And if he was sloppy then, how sloppy was he with these other cases?”

Fort Worth police Sgt. Pedro Criado on Friday characterized Williams’ error as “inadvertent” and said it was immediately corrected. He said investigators plan to revise the Carpenter warrant and pursue charges against the “correct person.”

Asked how Williams could have thought that the driver’s license photo of the 26-year-old Carpenter was that of the 19-year-old he swore he bought drugs from at least three times, Criado said: “I can’t answer what somebody was thinking at the time.” He said Williams would not be made available to explain.

Criado said Fort Worth police still intend to present the correct Carpenter’s case to the Tarrant County district attorney’s office along with those of the other suspects. That office will decide whether to take the case and, if so, whether to present the evidence to a grand jury.

According to a review by The Dallas Morning News of the 227 pages that make up the 19 arrest-warrant affidavits, Williams played a key role in all of them. A warrant was not needed for the arrest of the other suspects.

In the documents, Williams describes 47 hand-to-hand drug buys over 27 days from October through this month. In cases in which he didn’t make the buy, he accompanied the undercover officer who did. In all instances, he helped identify the suspects by looking at their driver’s license photos or license tags. He also relied on other sources for identification — for example, the online TCU football roster.

Melody McDonald, spokeswoman for the Tarrant district attorney’s office, did not directly address Williams’ credibility Friday; she said it was too soon to know how any of the cases would be dealt with.

“We are still waiting for the police to submit the case paperwork to us,” McDonald said. “We have not seen anything yet, so we can’t speculate on what is going to happen. Each case will stand on its own merits.”

Moore said that regardless of how Carpenter’s case is eventually handled — even if it’s never prosecuted — legal rules require that prosecutors inform the lawyers for all the other suspects about Williams’ misstep.

“I guarantee you the defense attorneys in the other cases will try to capitalize off the mistake the officer made in this case,” Moore said. “And if I was the prosecutor, I would be like, ‘Dude, how could you do this?’”

jtrahan@dallasnews.com

scrawford@dallasnews.com

AT A GLANCE: Four more suspects

Three additional arrests were made in Wednesday’s TCU drug sting, but the suspects’ names were not released as part of the original police reports. They are:

Jordan Michael Donaldson, 22, charged with possession of marijuana.

Cameron Jacob Forgie, 22, charged with possession of a controlled substance and possession of marijuana.

Eric C. Lodge, 22, charged with possession of a controlled substance.

Another suspect, Hunter McLaughlin, 24, surrendered Friday and posted bond on four counts of delivery of marijuana.